As oscillators and filters in the microwave frequency band, the YIG (Yttrium Iron Garnet) device is known. The YIG device utilizes the characteristics of yttrium iron garnet, which is a kind of ferrite, where Q values of the ferrimagnetic resonance are very high, which is suitable for use as microwave band variable tuning resonators and variable tuning oscillators.
The YIG device is used in the local oscillators and filters of measuring instruments, such as spectrum analyzers, network analyzer, etc, and is an important constituent part that plays an important role in the performance of these measuring instruments.
The principal element forming the YIG device is a YIG element. YIG crystal made of magnetic garnet material whose basic composition is expressed by the chemical expression Y3Fe5O12 is machined in a spherical shape to form the YIG element.
In the YIG device, it is required as a characteristic of the YIG crystal that the full width at half maximum of the magnetic resonance spectrum (hereinafter called “ΔH”) is small. The ΔH of the magnetic garnet material is generally expressed byΔH=ΔHi+ΔHp+ΔHa.Here, ΔHi is an intrinsic ΔH of the material having the same composition. ΔHp is a part contributed by demagnetizing fields around scratches, pores or different phases. ΔHa is a part contributed by internal magnetic fields based on crystalline magnetic anisotropy.
When the YIG crystal has lattice defects, the precession of the spins in the YIG crystal becomes disuniform, which results in RF characteristics degradation, such as decrease of the Q value, occurrence of parasitic resonance, and occurrence of spurious caused by them, etc. Accordingly, in the YIG device requiring the ΔH to be small, it is preferable to use the single crystalline YIG.
Patent Reference 1: Japanese published unexamined patent application No. Hei 09-270605
Patent Reference 2: Japanese published unexamined patent application No. Hei 06-236814
Patent Reference 3: Japanese published unexamined patent application No. Hei 08-165197
Patent Reference 4: Japanese published unexamined patent application No. Hei 10-233308